The invention relates generally to control systems, and more particularly to a power sharing system that provides power to a plurality of loads using a rechargeable power source to supplement line power in order to reduce a consumer""s peak usage used by a utility for setting a billing rate and to reduce overall usage of line power.
Currently, most consumers purchase their electrical power from a local supplier that has purchased bulk power from generation sources. Typically, the consumer pays a rate predicated upon a rate schedule. Rates on the schedule are generally higher during xe2x80x9cpeakxe2x80x9d time periods (e.g., periods falling between 6 AM and 11 PM when overall demand is higher) and lower during xe2x80x9coff-peakxe2x80x9d time periods (e.g., falling between 11 PM and 6 AM when overall demand is lower). Since most consumers use the majority of their electricity during peak time periods, most consumers pay an average rate which reflects the peak rate for the vast majority of their electrical power and are unable to avail themselves of the supplier""s off-peak rate.
In addition, the various rate levels during both peak and off-peak times are predicated on peak usage. This means that momentary xe2x80x9cspikesxe2x80x9d of power demand can cause a consumer""s rate for all of their usage to be billed at a higher rate. For example, if a consumer""s usage is more or less steady at level X but occasionally spikes to 3X for brief periods (e.g., when air conditioning, hot tubs, washer/dryers, well pumps, or other motor driven appliances first turn on separately or more than one at a time), the consumer""s rate for all power usage will be based on a rate for the 3X power level.
Accordingly, it is an object of the present invention to provide a system that lowers a consumer""s peak level of electricity usage in order to reduce the rate level used by a utility to set a billing rate.
Another object of the present invention is to provide a system that continuously supplies electrical power to a consumer using both a line source and a rechargeable source.
Still another object of the present invention is to provide a system that continuously supplies electrical power to a consumer using both a line source and a rechargeable source in a way that maximizes usage from the rechargeable source in order to reduce usage from the line source.
Yet another object of the present invention is to provide a system that controls the sharing of power from a line source and a rechargeable source and that is easily added to a consumer""s existing electrical infrastructure.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a power supply has a rechargeable DC source (e.g., batteries) coupled to an inverter/charger circuit that can convert a supplied AC voltage to a DC voltage to charge the batteries, and that can convert a DC output voltage from the batteries to an AC output voltage upon discharge of the batteries. A first switching means has an input port coupled to an AC voltage source and has an output port. The first switching means, programmable with at least one selected time period, couples the AC voltage source to the output port during a non-selected time period that is different than the selected time period and uncouples the AC voltage source from the output port during the selected time period. A second switching means is coupled to the output port for sensing thereon one of a normal AC voltage and an inadequate AC voltage. The second switching means has a switch coupled between the output port and the inverter/charger circuit. The switch is selectively placed in one of a first position when the normal AC voltage is sensed and a second position when the inadequate AC voltage is sensed. In the first position, the switch is positioned to so that the normal AC voltage is available across the switch and is supplied to the inverter/charger circuit as the supplied AC voltage. In the second position, the switch is positioned to receive the AC output voltage from the inverter/charger circuit as the DC batteries discharge. The AC output voltage from the inverter/charger circuit is available across the switch. A controlling means is coupled to the AC voltage source, the switch in its second position, and the plurality of loads. The controlling means includes a power source selector switch coupled to each load. Each power source selector switch can be positioned to be couple to one of the AC voltage source and the switch in its second position so that either the normal AC voltage or AC output voltage is available thereacross. The controlling means further includes a programmable means coupled to each power source selector switch to control a position thereof to maximize usage of the AC output voltage supplied by the power supply based on power requirements of the loads.